This project studies the structure and mechanisms of interaction of the oxidation-reduction pigments of the respiratory chain system, which is incorporated into the inner mitochondrial membrane of eukaryotic cells and the cytoplasmic membrane of bacteria. Several approaches are made. With the heart mitochondrial system we are investigating the interaction of soluble cytochromes c with different known structures with the oxidase complex, using both spectrophotometric and polarographic methods. These observations are compared with measurements of the reduction of the same cytochromes c by the NADH- and succinate-interaction sites on cytochrome c with the electron transport chain. We are investigating the 3-dimensional arrangement of the respiratory chain of Paracoccus denitrificans, an aerobic bacterium which synthesizes a resporatory chain system similar to that of eukaryotic mitochondria. It is easy to isolate membrane fragments bearing this system free of other membrane components. The reactions of the different members will be tested on addition of penetrating and non-penetrating substances as well as the effect of detergents and of varying the relative amounts of the different pigments by altering growth conditions.